Quantitative Risk Assessment Of FPSO-Topside About Fire Accident

Deep sea oil field and deep resources which were technically and economically infeasible are focused in recent year because resources comparatively easy to mine from land or shallow sea are almost on the brink of being exhausted. This leads to increase demand for offshore platform such as FPSO (Floating, Production, Storage and Offloading). An operation condition of the offshore platform is severe beyond comparison with platforms on land. A severe offshore environment condition may occur serious accident on the offshore platform. To prevent such accidents, many risk assessment analysis was conducting. Quantitative Risk Assessment (QRA) which is one method of risk assessment analysis. QRA is applied for various categories of industries. However, it is not enough for FPSO to apply this QRA yet. Fire which is one of the most important accident can lead to burn down of FPSO. Therefore, QRA of FPSO considering fire accident is mainly treated with ignition probability, leakage frequency and fire frequency in this paper.Ignition probability was calculated by using minimum parameters which were defined by expert judgments. In the step of modelling ignition probability, Event Tree Analysis (ETA) and Fault Tree Analysis (FTA) were adopted. Through these two methods, detection probability, discrete ignition probability and continuous ignition probability were calculated. When calculating these parameters, some parameters which were defined by expert judgments had to be used, however, uncertainties could increase in this case. Because of these reasons, reducing such parameters was mainly focused on during analysis to make minimum uncertainties. Newly suggested ignition probability analysis method was adopted on VLCC FPSO topside module. During adopting this method to VLCC FPSO topside module, two data which are time variant factor were needed and they can be taken by conducting leakage simulations. For this simulation, assumed leakage scenario on VLCC FPSO was used. When comparing this method with prior ignition probability method, result from adopted ignition probability model applied on VLCC FPSO topside module was relatively satisfied.Leakage frequency was analyzed based on database. There are a lot of companies and organizations where collecting accident statistics of offshore platform. Some database should be subscribed and other database are for free. They were simply introduced in this paper about the database which should be subscribed, and they were simply introduced with database in appendix about the database which are free. HCR System (HydroCarbon Release System) which is open source was mainly used to analysis leakage frequency on VLCC FPSO topside module. Paik et a. was also used this database system, however, they used relatively short period of database. HCR System currently has 23 years of database on offshore platform about leakage accident in UK shelf. In this paper, necessity of update of statistic was emphasized by comparing these two period of leakage frequencies. In the last part of this chapter, fire frequency based on above assumed scenario on VLCC FPSO topside module was calculated by multiplying calculated ignition probability in the chapter 2 and calculated leakage frequency in the chapter 3.Validation of Fire Dynamic Simulator (FDS) for use of offshore structures under the fire accompany wind was conducted in the chapter 4. The offshore structure used in the test was a floating production storage and offloading (FPSO) topside models with the wind-tunnel test used by B.J. Kim et al. Every case having various direction and speed of wind in their experiments was considered and validations were conducted by comparing the results from FDS with the experimental results. In the results, FDS has relatively high accuracy when the results were compared with the experimental results, and it is possible to replace for offshore structure experiments.In the chapter 5, bowtie method for risk assessment was adopted to FPSO topside module. Most of FPSO processes have continuous process, therefore, if a minor error occurs, whole process could be stopped. In addition, because already many FPSO have over 20 operation years, they can be easily exposed to risk of accident due to deterioration. Therefore, finding out more potential risk is important. Thus, bowtie risk assessment method was applied on FPSO by using BOWTIE THESIS software and the result was compared with original risk assessment method.